1. Field of the Invention
The present invention relates to internal combustion engines and straddle-type vehicles including the internal combustion engines.
2. Description of the Related Art
A conventionally known internal combustion engine (hereinafter referred to as an engine) of a vehicle such as a motorcycle includes a shroud for covering a portion of the engine, and a cooling fan for supplying air to inside of the shroud (see JP-A-2008-157222, for example). In such an engine, the cooling fan produces a flow of air inside the shroud. Thus, a portion of the engine is cooled by the air. This type of engine is idiomatically referred to as a “forced air-cooled engine”.
JP-A-2008-157222 discloses an air guide cover surrounding the entire peripheries of a cylinder block and a cylinder head of an engine, and a fan for introducing air to inside of the air guide cover. The cylinder block and the cylinder head are provided with fins. In a lower wall of the air guide cover, there is formed a cooling air outlet through which air inside the air guide cover is discharged downward. The air introduced into the air guide cover is divided into air flowing through a region above the cylinder block and the cylinder head, air flowing through a region rightward of the cylinder block and the cylinder head, air flowing through a region leftward of the cylinder block and the cylinder head, and air flowing through a region below the cylinder block and the cylinder head. The divided air, flowing through the region above the cylinder block and the cylinder head, reaches the region below the cylinder block and the cylinder head via the region rightward or leftward of the cylinder block and the cylinder head, and is then discharged downward through the cooling air outlet.
However, in the above-described conventional technique, the air guide cover covers the entire peripheries of the cylinder block and the cylinder head, and the air guide cover is thus increased in size, resulting in an increase in size of the engine.